1. Field of the Invention
The present invention relates to an acryl-based pressure-sensitive adhesive composition. More particularly, the present invention relates to antistatic pressure-sensitive adhesive compositions, and pressure-sensitive adhesive sheets and surface protecting films using the same.
Pressure-sensitive sheets comprising an antistatic pressure-sensitive adhesive composition of the present invention is suitably used in plastic products on which static electricity is easily generated. Among them, particularly, pressure-sensitive adhesive sheets of the present invention are useful as a surface protecting film (a protecting film) used for the purpose of protecting a surface of an optical member such as a polarizing plate, a wavelength plate, a retardation plate, an optical compensating film, a reflecting sheet, and a luminance improving film which are used as a liquid crystal display or the like.
2. Description of the Related Art
In recent years, upon transportation of optical appliances or electronic appliances and packaging of those parts on a printed board, individual parts are frequently transferred in the state where they are wrapped with a prescribed sheet, or in the state where they are applied to a pressure-sensitive adhesive tape. Among them, a surface protecting film is particularly widely used in the field of optical-electronic parts.
A surface protecting film is generally used for the purpose of preventing a scratch or a stain produced at processing or conveyance of a subject to be protected by applying to a subject to be protected via a pressure-sensitive adhesive layer coated on a protecting film side. For example, for the purpose of preventing a scratch or a stain, a surface protecting film is applied to an optical member such as a polarizing plate and a wavelength plate used in a panel of a liquid crystal display via a pressure-sensitive adhesive layer. When a liquid crystal display is produced with these optical members, since a surface protecting film become unnecessary, it is peeled and removed from an optical member.
In general, since the aforementioned optical member, pressure-sensitive adhesive, and surface protecting film are constructed of a plastic material, they have high electrical insulating property and generate static electricity upon friction or peeling. Therefore, also when a protecting film is peeled from an optical member such as a polarizing plate, static electricity is generated. When a voltage is applied to a liquid crystal in the state where static electricity remains, orientation of a liquid crystal molecule is lost, and a defect of a panel is generated.
In addition, static electricity is a great problem in a step of manufacturing a liquid crystal display or a touch panel. Due to this static electricity, there arises a problem that a dust is attached to a surface protecting film or an optical member, and this pollutes an optical member. Then, in order to prevent such the disadvantage, a surface protecting film is subjected to various antistatic treatments.
Previously, as an attempt to suppress the aforementioned electrification of static electricity, for example, a method of preventing electrification by adding a low-molecular surfactant to a pressure-sensitive adhesive, and transferring a surfactant from a pressure-sensitive adhesive to an adherend has been disclosed (for example, see Patent Publication 1). However, the low-molecular surfactant is easily bled on a surface of a pressure-sensitive adhesive layer and, when applied to a surface protecting film, staining of an adherend (a subject to be protected) is feared. Therefore, when a pressure-sensitive adhesive with a low-molecular surfactant added thereto is applied to a surface protecting film, there is a problem that optical property of an optical member is deteriorated.
In addition, pressure-sensitive adhesive sheets in which an antistatic agent is contained in a pressure-sensitive adhesive layer (for example, see Patent Publication 2) are disclosed. For preventing bleeding of an antistatic agent onto the surface of a pressure-sensitive adhesive in such pressure-sensitive adhesive sheets, an antistatic agent comprising a polyether polyol compound and an alkali metal salt is added to an acryl-based pressure-sensitive adhesive. However, even if such pressure-sensitive adhesive sheets is used, the bleeding of the antistatic agent etc. is inevitable, and as a result, there is a problem that upon actual application to a surface protecting film, there occurs a phenomenon wherein due to the bleeding with time or upon treatment under high temperature conditions, the surface protecting film is partially peeled off from the subject to be protected.
As described above, in any of these, the aforementioned problems can not be solved well-balanced yet and, in the technical field associated with electronic appliances where electrification or staining becomes a particularly serious problem, it is difficult to correspond to demand of further improvement of an antistatic surface protecting film.
[Patent Publication 1] JP-A No. 9-165460
[Patent Publication 2] JP-A No. 6-128539